package com.pastquestion;

public class Main11c {

	public static void main(String[] args) {
		int x = faci(20);
		System.out.println(x);
	}
	
	public static int faci(int n) {
		if(n == 1)
			return 1;
		return  faci(n  - 1) + 4*(n - 1);
	}
}
